This invention relates to a needle actuating mechanism of circular knitting machine such as fine gauge, high speed knitting machines for the production of stockings, socks and like tubular pieces of hosiery or garments, with or without the capability of creating patterns on the knitted fabric under electronic control. More specifically, the invention deals with an improved device for actuating a multiplicity of needles mounted to a rotary cylinder of such knitting machines for independent longitudinal displacement in its longitudinal direction.
In circular knitting machines of the class under consideration, a multiplicity of needles are slidably fitted in respective guide channels cut vertically in an upstanding, rotary knitting cylinder. Each needle is collinearly coupled to, or formed in one piece with, a shank having two butts formed in longitudinally spaced positions thereon so as to extend radially outwardly of the knitting cylinder. The two circumferential rows of butts are divided into groups of different lengths, which are arranged according to the particular piece of hosiery to be produced.
Heretofore, for imparting up and down motion to the needles on the knitting cylinder, there have been used a plurality of needle actuating cams arranged at circumferential spacings around the knitting cylinder. Each cam has a sloping cam surface which, when the cam is moved toward the knitting cylinder in rotation, makes relatively sliding engagement with the butts for raising or lowering the needles. Normally held retracted from the knitting cylinder by a return spring, each needle actuating cam has conventionally been forced toward the cylinder by very bulky and complex drive means against the bias of the return spring. Such drive means include, first of all, a bell crank having one arm held endwise against each needle actuating cam. The other arm of the bell crank is linked to a cam follower lever which in turn is biased against the contoured surface of a knitting cam in the form of a drum or cylinder as large in diameter as the knitting cylinder. The surface of the knitting cam in contoured to force each needle actuating cam toward the knitting cylinder in two steps. The prior art devie further requires means for driving the large knitting cylinders.
In operation, the knitting cylinders are driven intermittently as dictated by each knitting program for fabrication of the particular piece of hosiery. The needle actuating cams will then travel into and out of sliding engagement with the butts of the needles on the revolving knitting cylinder thereby selectively moving the needles up and down.
One objection to this prior art device is, of course, the huge bulk and the complexity of the various mechanical parts required for controlled operation of the needle actuating cams. Prohibitive costs have so far been required for the manufacture, assemblage, adjustment and maintenance of the known device. For this reason the known needle actuating mechanism has not lent itself to the fabrication of a great variety of products in limited quantities.
Another objection is that, since the needle actuating cams are driven by the cylindrical knitting cam, the knitting program has been limited in length to one complete revolution of the knitting cam. This limitation has imposed corresponding limitations upon the designs of the products to be knitted.
It has also been a drawback of the prior art that the needle actuating cams are subjected to great loading torque from the butts of the needles on the revolving cylinder as they travel into or out of sliding engagement therewith. The cams have therefore been susceptible to rapid wear or abrasion. When worn, the cams would fail to move the needles up and down as required, giving rise to errors in knitting operation.